When Brains Dream: Understanding the Science and Mystery of Our Dreaming Minds: Exploring the Science and Mystery of Sleep
Zadra, Antonio; Stickgold, Robert
Preface
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dreams are subjective events, invisible to all but the dreamer, unknowable to others except by the fragmented and often fuzzy recollections that a dreamer can tell us.
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our dreams are rarely driven by repressed desires. Dreams can, in a real sense, predict the future in a way that we can't when we're awake. Furthermore, dreaming has a cognitive basis; there are reasons for why our dreams feel so real and meaningful.
Chapter 1 Thinking About Dreams
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where do these thoughts, images, and emotions come from? How do they relate to the ones we have while we're awake? And why do we dream at all?
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Are dreams omens? Are they communications from the gods? Do they represent a truer and higher reality? And how do we understand their meaning? The answers to these questions put forth by our ancestors did more than influence people's beliefs about dreams; they profoundly affected how people perceived the human condition and our role in a largely unknown universe.
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dreams played a key role in the establishment of all major religions, in our conceptualization of the cosmos, the nature of death, and the ways in which the secular world can intersect that of the sacred and divine. In a very real sense, dreams have shaped our conception of the world, including our place within it.
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When the brain dreams, how does it create an experience of seeing, hearing, or feeling something that's as realistic as in waking life?
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Jean Piaget systematically investigated children's understanding of dreams as they grew up. What he found was that most preschoolers believed that dreams were real, originated from outside the dreamer, and could be seen by others. It wasn't until sometime between the ages of six and eight that most children grasped the idea that dreams were not only imaginary, but they could not be observed by others. And it was only around the age of eleven, according to Piaget, that children came to fully understand the nonphysical, private, and internal nature of dreams.
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in the fourth stage, the child (usually by ages eight to ten) fully understands that dreams are internal, private, and imaginary mental experiences.
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steps involved in attaining an adult-like conception of dreams remain the same: we first believe that dreams are part of the real world, then grasp their unreality, then their private nature, and finally locate the dream as taking place within our mind.
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Zhuangzi (369 BCE to 286 BCE). In his famous Butterfly Dream, he wrote:"Once upon a time, I, Zhuangzi, dreamt I was a butterfly, fluttering hither and thither, to all intents and purposes a butterfly. I was conscious only of my happiness as a butterfly, unaware that I was Zhuangzi. Soon I awakened, and there I was, veritably myself again. Now I do not know whether I was then a man dreaming I was a butterfly, or whether I am now a butterfly, dreaming I am a man."
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depending on individual circumstances, we can think of dreams as either real life (what Jessie believed about the duck and the confusion of narcoleptics); portals into equally real or alternate worlds; messages and prophecies from the gods; unfulfilled wishes; random brain noise; nocturnal entertainment; communications from the future, the dead, or other minds; sources of personal insights, problem solving, and creativity; or a window into memory processing.
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while we sleep, the brain is constantly working, processing our memories from the day just past. For every two hours we spend awake, taking in new information, it appears that the brain needs to shut down all external inputs for an hour to make time to figure out what it all means.
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It is only in the last few years, with 10-terabyte hard drives and the introduction of new artificial intelligence (AI) and "deep learning" programming techniques, that computers have begun to answer the question of what the information they collect means."
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you can never study someone else's dream experiences directly. All you have access to is the description of the experience the other person provides, whether it is shared verbally, in writing, through a drawing, or in a piece of performance art. Thus, the concept of dreams refers not only to "the series of thoughts, perceptions, or emotions that are experienced during sleep" but also to what people remember of these experiences and the spoken or written reports the dreamer eventually provides based on her (often short-lived) memory of the dream.
Chapter 2 Grasping at Dreams: Early Explorers of the Dream World
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thanks to Freud's dismissive view of their importance, studies that focused on things other than dreams "hidden" meanings were either forgotten or ignored as being of little interest.
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The researchers posed two central questions:"What mental faculties continue, stop, or change during sleep?" and "What is the fundamental difference between dreaming and thinking?" These were great, challenging questions at the time, and they remain central questions for today's modern dream research community.
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Maury hypothesized that unlike the waking brain, the dreaming brain didn't work as a synchronized, coherent whole and that faculties like perception, memory, will, and judgment could all fluctuate independently of one another. As a consequence, the dreaming mind could be pulled in different directions all at once, giving rise to bizarre and incoherent dreams. Thus, Maury believed, variations in our experiences during dreams were directly tied to how different regions of the brain functioned during sleep.
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Maury concluded that not only could our senses transmit information to the brain during sleep but also that the sleeping brain would, in turn, use that information to create a relevant dream. As anyone who has ever incorporated the sound of their alarm clock into a dream knows, he was absolutely correct.
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to be properly understood and interpreted, a dream had to be viewed as a mathematical sum: "The fundamental state of the dreamer (past experiences, intelligence, character, old habits) + the state of the moment (aspirations, passions, state of health, conditions of the organs and devices) + immediate experiences provoked by extrinsic conditions (during sleep)." 15 Today, 120 years later, we couldn't agree more.
Chapter 3 Freud Discovered the Secret of Dreams: or So He Thought
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Freud postulated the existence of a censor, a sentinel-like mechanism within the mind that kept unacceptable unconscious material from ever reaching conscious awareness during the day. During sleep, however, the sentinel became ineffective. It let down its guard, so to speak, allowing this unacceptable material to rise toward consciousness.
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A residual dream censor (known as the dreamwork) was therefore tasked with distorting the normally repressed unconscious material into unrecognizable form. Freud proposed four disguise mechanisms—condensation, displacement, considerations of representation, and secondary revision—which together carried out the dreamwork.
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Freud was unyielding in his belief that every dream was an attempt at wish fulfillment. In other words, no dream could materialize unless first infused with the psychic energy of a repressed wish.
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Freud saw dreaming as a relief valve for pathological desires. Jung, on the other hand, believed that dreams played a vital compensatory role in the development of a person's personality by presenting the dreamer with unconscious material that needed to be recognized (and integrated) for the dreamer to achieve a more balanced sense of self.
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while Freud wrote that dreams were "abnormal psychical phenomena" akin to neurotic symptoms, and while he emphasized their deceitful nature, Jung focused on dreaming as a wholesome, natural process and highlighted its creative, transcendent, and at times problem-solving nature.
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the view of Alfred Adler, mentioned earlier, that the manifest content of dreams was intimately tied to the dreamer's waking concerns and lifestyle, not to the unconscious as proposed by his mentor;
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Because Freud had made The Interpretation of Dreams the cornerstone of his psychoanalytic theory, it became virtually impossible to criticize his dream theory without calling into question the whole psychoanalytic enterprise.
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disagreements about the presumed functions of dreams were invariably diverted into quarrels about a host of other matters, such as the concept of repression, the nature of human memory, the origin of neurotic symptoms, models of childhood development, the clinical merits of free association, and the makeup of the unconscious as well as its presumed influence on everyday life. To some extent, this state of affairs still holds true today, and readers unfamiliar with the extreme virulence (some would say religious fanaticism) of these fights are invited to read up on the "Freud wars." 5 Even a cursory search will lead interested readers into some fascinating but decidedly poisonous literature.
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"except in extremely rare cases, it is impossible to verify the doctrine of the surly and somewhat egotistical Viennese author, who has always seemed more preoccupied with founding a sensational theory than with the desire to austerely serve the cause of scientific theory." 11
Chapter 4 The Birth of a New Science of Dreaming: Opening Windows onto the Sleeping Mind
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We now know that the brain's normally careful regulation of a host of bodily functions seems to go offline during REM sleep. Heart rate, blood pressure, and breathing all vary widely during REM sleep.
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Humans cycle in and out of REM sleep about every 90 minutes, all night long.
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we dream in all stages of sleep; we probably are dreaming most of the night, but more consistently in some stages and at some times than others; and, on average, our dreams are different from one sleep stage to another as well as from early to late in the night.
Chapter 5 Sleep—Just a Cure for Sleepiness?
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For every two hours we spend awake, storing away new information, our brain needs an hour of sleep to figure out the meaning and significance of that new information—an hour disconnected from the outside world and with the normal top-down mechanisms that guide our waking thoughts and actions turned off. That's the crucial task evolution has for sleep.
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Dreams don't replay memories exactly; they create a narrative that has the same gist as some recent memory and could have the same title.
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How we think about who we are is determined largely by our autobiographical memories of important events in our life, and sleep helps shape these memories.
Chapter 6 Do Dogs Dream?
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asking whether dogs dream. They certainly act like they're dreaming, and their brain activity while they're sleeping looks very similar to ours when we dream. But neither of these facts allows us to conclude that they're dreaming. We just can't tell.
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YOU MIGHT THINK that by now scientists would be able to tell when someone is dreaming without having to wake them up and ask. Unfortunately, we can't, although it's not a problem limited to dreaming. It's the whole consciousness problem again. We simply can't measure internal thoughts and feelings.
Chapter 7 Why We Dream
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The evidence comes from functional magnetic resonance imaging (fMRI) studies, which can record activity throughout the brain over several minutes or hours. With fMRI, the brain is divided into about 50,000 voxels—three-dimensional equivalents of your camera's two-dimensional pixels. Each voxel is a cube about a tenth of an inch on a side, and a snapshot of the activity in each of these voxels is taken every 2 or 3 seconds. Using an exciting new technique called multivoxel pattern analysis, researchers can determine the precise pattern of voxel activation produced in visual processing regions of the brain by a specific image, say, a picture of a baseball, or the average pattern of voxel activation for a category of images, for example, faces, tools, or doors. Then, using these classifiers, they can have a study participant look at pictures and reliably predict whether they're looking at a baseball, a face, or a door, entirely based on their pattern of brain activation.
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The patterns of brain activity that represent the images in our dreams are created by reactivating the patterns originally produced when we saw similar images in our waking life. Reactivations of other patterns of waking brain activity undoubtedly generate the brain patterns of thoughts and emotions that we experience in our dreams as well.
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it's important to distinguish between the uses we choose to make of the dreams we remember—for interpretation, personal growth, inspiration, or entertainment—and the biological or adaptive function of dreams.
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Dreams Have No Function Maybe, maybe not. A number of clinicians, philosophers, and dream researchers believe that dreaming serves no adaptive biological function at all. Owen Flanagan, a philosopher at Duke University, sees dreams as spandrels—unintentional side effects of evolution, like the sound of the heartbeat or the color of blood—that might nonetheless be useful when recalled. 13 David Foulkes, who has conducted some of the more intriguing studies of dreaming in children, maintains that dreaming does not have a biological function. 14 The eminent dream researcher and theorist William Domhoff, who has spent decades compiling well-founded research showing that psychologically meaningful information can be extracted from people's dream reports, has nonetheless argued that dreaming was not conserved by natural selection although dream recall, like the capacity to generate music, can play a significant role in people's lives. 15 Similarly, some researchers working on the relations between sleep and memory have suggested that while dreams may reflect underlying processes of memory reactivation and evolution, the dreams themselves serve no function. For some of these researchers and many others, dreaming is nothing more than a meaningless epiphenomenon of the sleeping brain.
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In the model we propose in the next chapter, dreaming is a form of sleep-dependent memory processing, albeit a phenomenologically complex one, that extracts new knowledge from existing information through the discovery and strengthening of previously unexplored associations. In doing so, dreams rarely replay active concerns directly or offer concrete solutions to them. Rather, they identify and strengthen associations that in some way embody these concerns and that the brain calculates may be of use in resolving them or similar concerns, either now or in the future.
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the sleeping brain performs multiple forms of memory evolution. It selects recent salient memories for nocturnal processing, prioritizing emotional memories but also processing unemotional ones; it stabilizes and strengthens some memories while extracting rules and gist from others; and it integrates new memories into older, preexisting knowledge networks. Fortunately, the brain is great at multitasking and can probably carry out multiple forms of memory processing at the same time.
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Dreaming creates narratives that unfold in our minds across time and allows us to experience the thoughts, sensations, and emotions engendered by those narratives. Dreaming, like waking consciousness, allows us to imagine sequences of events, to plan, to plot, to explore.
Chapter 8 Nextup
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NEXTUP proposes that dreaming is a unique form of sleep-dependent memory processing that extracts new knowledge from existing memories through the discovery and strengthening of previously unexplored weak associations.
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The brain then combines the memories into a dream narrative that explores associations the brain would never normally consider. In doing so, NEXTUP searches for and strengthens the novel, creative, insightful, and useful associations discovered and displayed in our dreams.
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At one extreme, Freud's disguise-censorship hypothesis explained bizarreness in dreams as part of an intentional process of disguising forbidden wishes that weren't safe to express directly in dreams.
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Pharmacologically, lysergic acid diethylamide (LSD) works by activating serotonin receptors, including serotonin 1A receptors, which in turn can block the release of serotonin in parts of the brain. All the weirdness of LSD—the hallucinations and acid insights and everything else—may be a direct consequence of this biochemical blockade of serotonin release. This obviously isn't the normal state of affairs in the brain. But there is one time every day when serotonin release is completely blocked, and that's during REM sleep. We dream in both REM and non-REM sleep, but the most bizarre, emotional, and unlikely dreams—and arguably those that seem most meaningful to us—occur in REM sleep. The reduction in serotonin levels during non-REM sleep (relative to wakefulness) and the complete cessation of its release during REM sleep may serve the important role of shifting the brain's bias toward assigning more value than it otherwise would to those weak associations activated during dream construction. This chemical action may be the grease that enables these potentially useful new associations to slide into our repertoire of valuable insights, and in so doing produces a felt sense of meaningfulness.
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when brains dream in REM and non-REM sleep, they're doing things differently—and they suggest that the two types of dreams are performing different functions.
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the brain areas that turn off whenever we start to carry out a mental task are the regions that do whatever the brain does when we're "not doing anything." Together these regions make up the default mode network (DMN), whose discovery has helped us appreciate just how true it is that the brain never rests.
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When we look at the brain regions that make up the DMN, we find a sub-network that monitors the environment for important changes, watching out for any danger. Keeping us safe is probably one function of the DMN. But we also find a sub-network that helps us recall past events and imagine future ones, another that helps us navigate through space, and yet another that helps us interpret the words and actions of others. And these are the mental functions associated with mind wandering. Much of mind wandering involves hashing over the events of the day or anticipating and planning future events. Indeed, such planning has been proposed as a function of mind wandering. 5 So it's perhaps not surprising that mind wandering is associated with increased activity in the DMN. 6 This appears to be a second function of the DMN.
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William Domhoff and his colleague Kieran Fox have gone so far as to suggest that dreaming, or at least REM sleep dreaming, constitutes a brain state of "enhanced mind wandering." 8 More recently, Domhoff has proposed that the neural substrate of dreaming lies within the DMN.
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The hypnagogic period is a unique link between pre-sleep mind wandering and early sleep dreaming. A"fracture point" often takes place in sleep-onset mentation, wherein rational waking thoughts—inevitably about waking concerns or incomplete mental processes—shift into hypnagogic dreams.
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Hypnagogic dreams are usually less bizarre and much less emotional than dreams from later in the night, and they often lack two features that are almost always present in other dreams; namely, self-representation and narrative structure. Much of the time these dreams are just unusual thoughts, or a random geometrical pattern, or a simple picture, like a landscape or a face.
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brief hypnagogic dreams appear to extend the DMN's work into the sleep period, identifying and tagging current concerns for further sleep-dependent processing, and perhaps then beginning to identify associated memories for later consideration. But the very briefness of such dreams suggests that they can do little more than tag these memories, leaving more extensive processing for later in the night.
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as first the Walkman and then the iPhone came to dominate our free time, the DMN has slowly been squeezed out of our daily lives.
Chapter 9 The Mischievous Content of Dreams
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Whether they contain visual, auditory, tactile, olfactory, vestibular, or other sensory modalities, dreams are typically intensely vivid and compellingly realistic. In fact, except for those rare occasions when we dream lucidly, we always believe our dreams to be real while we're in them, and we only come to realize their illusory nature after we wake up.
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Most dreams with sensory perceptions contain visual images; sounds are reported only about half the time; and reports of smell, taste, and pain are each seen in less than 1 percent of reports.
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NEXTUP proposes that dreaming enhances memory processing by allowing the brain to create narratives related to ongoing concerns and allowing the dreamer to react to them. Narrative sequences are so common in dreams10 that we don't even think about it; it's just what dreams are. Dreams could have evolved to simply display visual images, like looking at pictures, but instead they have evolved to flow through time as if we were awake.
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the DMN is involved with recalling past events and imaging future ones while we're awake—as a veritable "story-telling" instinct.
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dreams usually present us with convincing settings and characters, and it's often a conversation, situation, or unfolding of the plot we find ourselves in that is most strikingly odd. The same can also be said for many plays, novels, and movies.
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dreams contain convincing sensory experiences embedded in a narrative story with moment-to-moment, but not beginning-to-end, continuity. They are characterized by bizarreness, nearly omnipresent feelings or emotions, self-representation, and an embodied sense of self.
Chapter 10 What do We Dream About? and Why?
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about 60 percent of recurrent dreams have the dreamer dealing with a challenge or threat, either psychological or physical. If the dreamer is being chased or otherwise confronted, the hostile agents in children's recurrent dreams usually involve fictional or folkloric characters, such as monsters, witches, zombies, and ghoulish creatures; adult recurrent dreams, on the other hand, typically feature human characters, including burglars, strangers, mobs, and shadowy figures.
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Parasomnias are a class of mostly unpleasant experiences or behaviors that often occur on the edges of sleep, such as hypnagogic jerks (sudden twitches or feelings of falling as you're falling asleep) or instances of sleep paralysis, discussed in Chapter 4, that typically occur as you're waking in the morning.
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Of course, in our dreams, these lists of associated memory elements are not presented as tables or lists. Instead, they are incorporated into embodied dream narratives. The use of narrative is not surprising; we use it in waking as well. Whether in movies or books or simply in storytelling, humans use dramatization, with its similes, figurative plots, and metaphors, to describe and present the emotional events and concerns of our lives. What our brains do while dreaming is not that different from what they do when we go to the theater—they imagine and explore possibilities embedded in a narrative with the hope of gaining new understandings about ourselves and the world we live in.
Chapter 11 Dreams and Inner Creativity
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My mental eye, rendered more acute by the repeated visions of this kind, could now distinguish larger structures of manifold conformation: long rows sometimes more closely fitted together all twining and twisting in snake-like motion. But look! What was that? One of the snakes had seized hold of its own tail and the form whirled mockingly before my eyes.
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many of these iconic dreams came from the hypnagogic period, after pondering a problem shortly before sleep. As we discussed earlier, the physiology of the hypnagogic state, its dream content, and the function of its dreams are all unique to that state. Its physiology is more directly linked to prior waking physiology, and its dreams reflect current waking concerns more strongly than later sleep stages. Indeed, the hypnagogic period has been exploited precisely for its ability to reflect creatively on such concerns.
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The true creativity found in dreaming is in the creative exploration of associative neural networks, in which our brain ferrets out normally weak associations that are of potential value in addressing these problems.
Chapter 12 Working With Dreams: Ideas, Methods, and Caveats
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let's start by getting one thing out of the way: We don't know what your dreams mean and, we believe, neither does anybody else. By this, we don't mean to suggest that dreams are devoid of substance—this book details many ways that dreams can be viewed as psychologically meaningful creations of the brain. But we do take issue with the notion that behind every dream lies one "true" meaning, and that this singular interpretation can be deciphered by specially trained or gifted individuals.
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desire to make sense of our dreams—to understand what they mean—has probably been around since our ancestors first started remembering their ethereal nightly reveries.
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Therapists choosing to integrate dreamwork into their practice must decide how they want to do this. For some, the idea of dream interpretation is inherently tied to Freudian dream theory and the need to retrace the dream back to unconscious conflicts and desires. For others, working with dreams implies mastering Jungian ideas of how dreams are structured by myths, archetypes, and both personal and collective levels of the unconscious. In Gestalt-based approaches, different dream elements are understood as projections of both accepted and disowned aspects of the dreamer's personality. Other approaches focus on the emotions experienced during dreams, on interpersonal relations depicted in dreams, on bodily sensations experienced while retelling a dream, and so on. Dozens of techniques and schools of thought are aimed at using dreams for greater self-understanding, each with distinct clinical and theoretical underpinnings.
Chapter 13 Things That Go Bump in the Night: PTSD, Nightmares, and Other Dream-Related Disorders
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sleep is an amazingly complex process that requires a wide range of brain systems to function in carefully coordinated patterns of activity.
Chapter 15 Telepathic and Precognitive Dreams: or Why You May Have Already Dreamt of This Chapter
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DREAMS OF MIND READING. DREAMS OF EVENTS unfolding far away. Dreams that foretell the future. It seems like everyone either has had one of these dreams or knows someone who has. Other than being of interest since time immemorial and well ingrained in our cultural ethos, telepathic and precognitive dreams are the experiences that raise the most questions—and passionate debates—about the stranger, seemingly inexplicable side of dreaming.
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If you've ever had one of these precognitive (seeing the future) dreams, or one involving telepathy (communicating with someone directly from mind to mind) or clairvoyance (observing events not actually perceivable), you know how hard it is to shake the feeling that something particularly mysterious—beyond the bounds of normal science—has happened.
Epilogue What We Know, What We Don't Know: What We Might Never Know, and Why It All Matters
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When your brain constructs a dream, it creates an amazingly comprehensive virtual world within your mind. It generates illusory sensory experiences that are often indistinguishable from those generated by your sensory organs when you're awake.
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As your dreaming brain activates the neural maps that underlie both your sense of self and your understanding of the world, you experience and constantly interact with a rich, immersive, and multifaceted sensory dream world as it unfolds over time, and you do so from a very personal, first-person perspective. Because your brain typically populates this dream world with people, creatures, pets, and other objects you can interact with, you also experience more socially oriented feelings such as envy, sympathy, camaraderie, shame, arrogance, and pride. Not only that, but when your brain dreams, it also tricks you into believing that the other people inhabiting your dreams are also experiencing such feelings.
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we still don't really know how the brain picks the memories to use in constructing a given dream. We don't know if the face of the stranger in our dream comes from stored memories, for which we've just forgotten the context, or are constructed on the fly by putting together individual features from an assortment of memories. We're not sure what guides the behaviors, feelings, and personalities ascribed to the characters in our dreams. We don't know how the narrative structure of the dream is woven into a whole, or how emotions are brought into these narratives. And we have no idea how this entire process rises to consciousness in the form of dreams.
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NEXTUP suggests that the function of dreaming is to explain the past and predict the future, to discover what's "next up" in our lives. This is the brain's task while we dream.
Appendix—Nextup: A Model of How and Why We Dream
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Dreaming is a unique form of sleep-dependent memory evolution, one that extracts new knowledge from existing information through the discovery and strengthening of unexpected and often previously unexplored associations.
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Dreams don't replay events from our life the way they're replayed when we remember them during the day. Instead, they tell stories about the event. B. Dreams bring together fragments of both episodic and semantic memories. C. Complete episodic memories aren't incorporated into dreams, and direct reference to or incorporation of current concerns is rare.